Achieving High Speed and Precision

Customized Solutions for Machine Builders

Real improvement in machine performance is the goal for Moog when developing a solution for our customers. A machine builder named Morphic Technologies (http://www.morphic.se),  based in Sweden, is an ideal example of Moog’s ability to design a custom solution that achieves vastly better results than have ever been experienced with their machine. This was accomplished through a partnering relationship that involved applying experience in motion control, and using custom hydraulic and electric products in a wire cracking machine. The challenge in this application involved achieving very high speeds and precise accuracies to create parts that are perfect every time.

The expertise of Moog’s global engineering organization in hydraulic, electric, and hybrid technology was a perfect match for Morphic Technologies as their machine has a hydraulic impact axis and an electric feeding axis. A special customized servomotor and the new high performance DS2100 servodrive were used for the electric axis that controlled the speed of the machine. In addition, the Moog Servo Controller (MSC) was the perfect product to control the three high performance axes. The MSC also proved to be a money-saver as Morphic was able to eliminate the existing PLC. Most importantly, the ultimate solution not only met, but exceeded the customer’s demanding project goals.

The Application

The core competency of Morphic Technologies is the development of technology and systems for precision steering of extreme dynamic forces. One of its premier products is a wire cracking machine that is used by manufacturing facilities around the world for high quality wire cracking. The principle of operation for this machine is a metal wire that is fed through two tight fitting rings with orifices aligned in a row (cracking dies). One of these dies is hit with a huge impact (comparable to a hit with a hammer), while the other is kept in position. This causes the wire inside to crack due to the huge shock impact. Although the impact may cause only a movement of 1 mm, a wire of even 25 mm in diameter will crack through immediately. The result is a perfect surface instead of a traditional shear cut.

The Challenge

The challenge for the Moog - Morphic partnership was to create a machine capable of cracking wires up to 25 mm in diameter at the incredible speed of 800 to 1000 pieces per minute (The sound created is similar to a machine gun). Also required was precise control to allow maximum flexibility for wire size, impact control, feeding length, and accuracy. This way the cutting machine can be sized correctly and does not need to be oversized. The control of the impact provides quality control, extended lifetime of the tools, and higher reliability for users.

These technical objectives were achieved and improved upon with the Moog solution. Due to the flexibility of the Moog Servo Controller (MSC) in providing motion and sequence control, the existing PLC was eliminated and all operations are now controlled through by the MSC and one operator's panel. This is unique for cutting machines and enables quicker setup and easier adjustments for cutting length, speed or impact force. The overall package is easier to use, more productive, and highly flexible.

Hydraulic Impact Axis

Moog Products:

  • MSC for control
  • RKP Pump -Radial Piston Pump
  • Servo-Proportional Flow Control Valve

For optimal cutting quality and performance, the kinetic energy from the impact ram needed to be controlled. The optimal energy level depends on the type and profile of material, which can range from soft copper to hardened steel. The impact itself is created by a fast and precisely controlled hydraulic cylinder. The Moog Servo-Proportional Valve controls a special valve developed by Morphic (patent app.) arranged inside the cylinder. This allows for 100% step response in only 5 ms. For optimum timing, the movement needs to be damped immediately after the hit and moved back to original position to allow further feeding of the wire. The complete movement (impact, damping and move back) is realized in less than 20 ms.

Electric Feeding Axis

Moog Products:

  • Two customized G400 Series *Servomotors with Stegmann Absolute Encoder (SRM50)
  • Two new DS2100 Servodrives
  • MSC for control

The feeding unit is vital as it defines the speed capability of the machine. Two clamping units feed the wire alternately and each is controlled by a rack and pinion system using two Moog G400 series servomotors. The project specification was to achieve a continuous duty cycle (clamping, acceleration, deceleration, fine positioning) in only 80 ms, and to obtain fine positioning accuracy of 0.05 mm.

To achieve this speed, a special custom servomotor was optimized for the application. The customization allowed for the motor to be directly coupled to the actuator, removing the need for a gearbox. It also provided for the necessary high levels of torque needed to overcome the high inertia forces for acceleration and deceleration. To realize the required accuracy a high resolution feedback device was required, so the servomotors were equipped with a Stegmann encoder (SRM50) instead of the traditional resolver. The encoder delivers both commutation and absolute position signals.

The very fast position control loop of the electrical axis is closed inside Moog’s new high performance DS2100 Servodrive. This powerful and flexible servodrive provides a wide range of interface options, which included the necessary interface to the high resolution optical encoder. Tests performed with this machine resulted in an absolute error less than 0.001 mm within 150 ms. The target 0.05 mm accuracy was reached with a duty cycle time of only 60 ms.

Moog’s solution realized the accuracy of 0.05 mm and speed of only 60 ms for a 50 mm movement with a fine positioning accuracy that was even better than required. This is a new record in speed.

Machine Control with Moog Servo Controller (MSC)

Moog Products:

  • Moog Servo Controller (MSC)
  • Moog Axis Control Software (MACS) development environment
  • QAIO and QDIO, input-output extension modules

Morphic needed to find a more powerful machine controller for the high performance axis. The Moog MSC was the perfect answer as it even had enough processing power to handle other “miscellaneous” PLC functions. The MSC is now the only control inside the machine for both PLC and Motion Control. Specifically it controls the following functions

  • High performance hydraulic axis
  • Two high performance servomotor axes
  • User interface, keyboard, and terminal
  • Various input switches and signal lights
  • Safety switches and monitoring sensors
  • Temperature control
  • Hydraulic pump and pressure control with oil temperature monitoring
  • Preheating zone for wire

To realize all these features the MSC needed extended I/O’s, which are available as click-on modules from Moog’s M3000 System portfolio. All the M3000 modules are software configurable. Morphic chose one QAIO (analog I/O) and two QDIO (digital I/O) modules.

All high speed motion controls, as well as all the PLC functionality in the machine, are controlled by the Moog Axis Control Software (MACS). Morphic’s staff implemented the machine control software easily, even without any formal training, as they knew the IEC61131 languages upon which the MACS is based. Using the Moog function blocks and Moog’s PLCopen motion library made their task even easier.

Summary

Morphic Technologies’ cutting machine is a truly unique product in the market, largely due to its approach to control. Through innovation, the company delivered a fast and accurate machine to meet their customers’ needs. Moog worked together with Morphic to apply its expertise in motion control and develop custom versions of its high performance servomotors and servodrives.

Moog is equally skilled in providing motion control solutions in hydraulic, electric or combined technologies. The effective implementation of the easy-to-use Moog Servo Controller was another key component to an overall solution that not only met, but exceeded the expectations of the demanding application - an accuracy of 0.05 mm and speed of only 60 ms. Breaking records is routine for world class partners like Moog and Morphic.

Appendix A

Machine Location and Description of Wire Cracking Machine

  • Left: Wire feeding (straightening unit removed)Wire size up to 25 mm in diameter
  • Middle Left: High performance electrical feeding unitFeeding distance used: 40 mm (but can be higher)Feeding accuracy: +/- 0,05 mmCycle time per feed: approx. 60 msec
  • Middle Right: Wire heating unit: Required for hardened wires
  • Right: Human machine interface with monitor and keypad etc.Hydraulic cracking unit is located vertically behind the monitor (cycle time for movement approx. 20 ms)

About the Author

Jürgen has been working with Moog for more than 11 years, starting with servomotors and servodrive engineering and later heading the Moog GmbH Research and Development Department. Today he has worldwide responsibility for Moog’s Industrial Controls product line. He has a University degree in Electronics (Diplom Ingenieur).